The present invention relates to a process for the selective manufacture of methyl ketones of the formula ##STR1## by oxidation, in liquid phase, of olefins of the formula R--CH.dbd.CH.sub.2. R is alkyl, aryl, aralkyl or alkylaryl hydrocarbon radicals having from 1 to 20 carbon atoms. Non-limitative examples thereof are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, styrene, and the like.
The method, according to the invention, for manufacturing methyl ketones consists of operating in the presence, on the one hand, of a specific palladium catalyst as defined below and, on the other hand, of an oxidizing agent which is either hydrogen peroxide or a carefully selected organic hydroperoxide.
In the known processes of the Wacker Type, wherein carbonyl compounds are synthesized from olefins, the catalytic system is usually formed of two associated metals, one of them being usually palladium, the other being usually copper or iron, the two metals being used as halides, particularly as chlorides. This catalytic system can be used with water which is the main source of the oxygen incorporated in the ketone.
These processes have however the disadvantage to operate in a very corrosive concentrated hydrochloric acid medium and to necessitate special alloys. Moreover, they are selective only for the oxidation of light olefins such as ethylene and propylene. The production of methylketones from heavier olefins usually results in the formation of undesirable chlorinated materials and aldehydes. Improvements have, however, been brought to the selectivity, when oxidizing heavy olefins, for example, by using organic solvents (French Pat. No. 1,564,635 or U.S. Pat. No. 3,410,807) however the disadvantages associated to the use of the bimetallic system are not avoided.
Other known processes are disclosed in the U.S. Pat. Nos. 3,932,521 and 3,370,073 concerning the oxidation of olefins in the presence of oxygen and a catalyst selected from the group consisting of palladium sulfate, the palladium halides, palladium phosphate and palladium acetate, or a Pd+HCl system. These processes are themselves not sufficiently selective, particularly when using palladium halides or hydrochloric acid.